To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 80 (MBC+), indicating that it is in quite good shape.

2. Previous Auction Prices: By looking at the auction prices of coins with a similar condition (80), we can see that they have varied, but there are several examples that give us an idea of the price range:
- In previous auctions, coins with a condition of 80 have reached hammer prices of up to 770 euros (as in the auction on October 21, 2020).
- Other hammer prices for coins with a condition of 80 have been 280, 260, 220, and 300 euros.

3. Average Hammer Price: The average hammer price for this coin is 327.65 euros, which is also a good indicator.

4. Starting Price: The current starting price is 200 euros, which is reasonable compared to previous hammer prices.

Based on this data, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the condition is good and there are precedents of high hammer prices in the past.

Therefore, an estimated maximum purchase price could be approximately 500 euros.